Instructions  to  Inspectors 

ON 

Reinforced  Concrete 
Construction 

BY 

GKO.  P.  CARVER 

Lately  Division  Engineer 
Florida  East  Coast  Ry.  Key  West  Ext. 


PUBLISHED  BY 

PAYSON  PUBLISHING  CO., 

Bank  Bounding,  Beverly,  Mass. 


UNIVERSITY  OF  ILLINOIS 
LIBRARY 


Class 


Book 


Volume 


Je  07-10M 


Instructions  to  Inspectors 

ON 

HIP'  !  \  '(  1  /  / 

Reinforced  Concrete 
Construction 


B\\ 

GKO.  P.  CARVER 

Lately  Division  Engineer 
Florida  East  Coast  Rv.  Key  West  Ext. 


PRICE  50  CENTS 


PUBLISHED  BY 

PAYSON  PUBLISHING  CO., 

Bank  Building,  Beverey,  Mass. 


Copyright  1900  by  G .  P.  Carver 


Reinforced  Concrete  Construction. 


PREFACE. 

In  the  preparation  of  this  little  book  the  write 
has  tried  to  set  forth  in  detail  the  duties  of  an  ii 
spector  on  reinforced  concrete  construction.  Pai 
of  these  instructions  are  taken  from  Instructions  t 
Inspectors  on  Reinforced  Concrete  arch  construe 
tion  prepared  by  the  writer  for  use  on  the  viaduc 
work  of  the  Key  West  Extension  of  the  Florid 
East  Coast  Railway,  on  which  work  the  writer  wa 
engaged  as  a  division  engineer  in  charge  of  th 
Kong  Key — Conch  Key  viaduct,  which  is  two  mile 
in  length  and  composed  of  180  semi-circular  arclie 
of  50  feet  span  constructed  between  two  of  th 
Florida  Keys  in  a  depth  of  water  varying  from  0  t 
10  feet. 

There  are  many  of  the  instructions  given  fcj 
this  work  that  are  applicable  to  building  construe 
tion  and  practically  any  type  of  reinforced  concret 
structure. 

The  instructions  under  the  head  of  buildin 
construction  were  prepared  by  the  writer  for  tlr 
use  of  the  inspectors  on  the  construction  of  th j 
United  Shoe  Machinery  Co.  plant,  a  group  of  mam 
facturing  buildings  in  Beverly,  Mass.  This  plan 
is  composed  of  about  ten  buildings  all  of  reinforce- 
concrete  and  is  probably  the  largest  plant  of  build 
ings  of  this  construction  in  the  world.  The  write| 
was  the  engineer  for  the  owners  during  the  con 
struction  of  the  plant. 

It  is  hoped  by  the  writer  that  these  instruction 
based  on  the  experience  gained  by  him  in  this  fori 
of  construction  will  be  of  direct  value  to  engineer 
and  contractors  engaged  in  the  inspection,  super 
vision  and  construction  of  reinforced  concret 
structures. 

GEORGE  P.  CARVER, 

Beverly,  Mass. 


February*  1907. 


Reinforced  Concrete  Construction 


Reinforced  concrete  construction  requires  rigid  in¬ 
jection,  continuous  and  intelligent  supervision. 

Careful  proportioning,  mixing  and  compacting  of 
le  materials  is  necessary. 

To  omit  or  misplace  the  reinforcement  will  cause 
ifective  or  even  destructive  results. 


Inspection  of  Cement 

A.s  recommended  by  the  American  Society  for  Testing 
Materials.) 


All  cement  shall  be  inspected. 

Cement  may  be  inspected  either  at  the  place  of 
lanufacture  or  on  the  work. 

In  order  to  allow  ample  time  for  inspecting  and 
^sting,  the  cement  should  be  stored  in  a  suitable 
eather-tight  building  having  the  floor  properly 
locked  or  raised  from  the  ground. 

The  cement  shall  be  stored  in  such  a  manner  as  to 
irmit  easy  access  for  proper  inspection  and  identifi- 
ition  of  each  shipment. 

Every  facility  shall  be  provided  by  the  contractor, 
id  a  period  of  at  least  twelve  days  allowed  for  the  in¬ 
jection  and  necessary  tests. 

Cement  shall  be  delivered  in  suitable  packages, 
ith  the  brand  and  name  of  manufacturer  plainly 
arked  thereon. 

A  bag  of  cement  shall  contain  94  pounds  of  cement 
fct.  Each  barrel  of  Portland  cement  shall  contain 
>ur  bags,  and  each  barrel  of  natural  cement  shall 
mtain  three  bags  of  the  above  net  weight. 

Cement  failing  to  meet  the  seven-day  reauire- 
ents  may  be  held  awaiting  the  results  of  the  twenty  - 
ght  day  tests  before  rejection. 

The  acceptance  or  rejection  shall  be  based  on  the 
flowing  requirements: 

98264 


Reinforced  Concrete  Construction. 

PORTLAND  CEMENT. 

Definition.  This  term  is  applied  to  the  finely  pul¬ 
verized  product  resulting  from  the  calcination  to  in¬ 
cipient  fusion  of  an  intimate  mixture  of  properly  pro¬ 
portioned  argillaceous  and  calcareous  materials,  and 
to  which  no  addition  greater  than  3  per  cent,  has  been 
made  subsequent  to  calcination. 

SPECIFIC  GRAVITY. 

The  specific  gravity  of  the  cement,  thoroughly 
dried  at  100  degrees  C.,  shall  be  not  less  than  3.10. 

FINENESS. 

It  shall  leave  by  weight  a  residue  of  not  more  than 
8  per  cent,  on  the  No.  100,  and  not  more  than  25  per 
cent,  on  the  No.  200  sieve. 

TIME  OF  SETTING. 

It  shall  develop  initial  set  in  not  less  than  thirty 
minutes,  but  must  develop  hard  set  in  not  less  than 
one  hour,  nor  more  than  ten  hours. 

TENSILE  STRENGTH. 

The  minimum  requirements  for  tensile  strength 
for  briquettes  one  inch  square  in  section  shall  be  with¬ 
in  the  following  limits,  and  shall  show  no  retrogres¬ 
sion  in  strength  within  the  periods  specified: 

Age.  NEAT  CEMENT.  Strength,: 

24  hours  in  moist  air . 150-200  lbs 

7  days  (1  day  in  moist  air,  6  days  in 

water)  . 450-550  lbs 

28  days  (1  day  in  moist  air,  27  days  in 

water)  . 550-650  lbs 

ONE  PART  CEMENT,  THREE  PARTS  SAND. 

7  days  (1  day  in  moist  air,  6  days  in 

water)  . 150-200  lbs 

28  days  (1  day  in  moist  air,  27  days  in 

water)  . 200-300  lbs 


4 


Reinforced  Concrete  Construction. 


CONSTANCY  OF  VOLUME. 

Pats  of  neat  cement  about  three  inches  in 
diameter,  one-half  inch  thick  at  the  centre,  and  taper¬ 
ing  to  a  thin  edge,  shall  be  kept  in  moist  air  for  a 
period  of  twenty-four  hours. 

(a)  A  pat  is  then  kept  in  air  at  normal  tempera¬ 
ture  and  observed  at  intervals  for  at  least  28  days. 

(b)  Another  pat  is  kept  in  water  maintained  as 
near  70  degrees  P.  as  practicable,  and  observed  at  in¬ 
tervals  for  at  least  28  days. 

(c)  A  third  pat  is  exposed  in  any  convenient  way 
in  an  atmosphere  of  steam,  above  boiling  water,  in  a 
loosely  closed  vessel  for  five  hours. 

These  pats,  to  satisfactorily  pass  the  requirements, 
shall  remain  firm  and  hard  and  show  no  signs  of  dis¬ 
tortion,  checking,  cracking  or  disintegrating. 

SULPHURIC  ACID  AND  MAGNESIA. 

The  cement  shall  not  contain  more  than  1.75  per 
cent,  of  anhydrous  sulphuric  acid  (S03),  nor  more 
than  4  per  cent,  of  magnesia  (MgO). 


5 


Reinforced  Concrete  Construction. 


INSTRUCTIONS 


IN  GENERAL. 

Inspectors  will  be  required  to  become  familiar  with 
and  carefully  follow  out  the  following  instructions  re¬ 
garding  inspection  and  see  that  the  work  is  carried 
out  in  strict  accordance  with  same,  ^.n  inspector  will 
be  required  to  be  on  the  work  during  the  setting  of 

forms,  placing  of  reinforcement  and  the  mixing  and 

placing  of  concrete.  He  will  represent  the  Lngineer- 

in  ^Charge,  and  will  be  held  responsible  for  the  correct 
performance  of  the  work  assigned  to  him.  He  will,  in 
a  general  way,  carefully  and  continuously  watch  the 
progress  of  the  work,  making  a  record  of  the  amount 
of  work  done  each  day  and  the  manner  an  which  it  is 
done. 

He  will  be  required  to  become  thoroughly  familiar 
with  the  plans  of  the  work  which  he  is  inspecting, 
that  he  may  intelligently  perform  the  duties  intrusted 
to  him.  He  will  be  required  to  fill  in  a  daily  report 
sheet,  printed  forms  being  furnished  for  this  purpose, 
giving  the  location  of  the  work,  the  amount  of  work 
done,  the  number  of  batches  mixed  and  placed,  the 
proportions  used,  the  arrival  of  material  and  all  such 
other  information  as  will  assist  in  making  a  concise 
and  accurate  record  of  the  progress  and  cost  of  the 
whole  or  any  part  of  the  work. 

A  book  will  be  furnished  the  inspector,  in  which  a 
record  will  be  kept  of  the  progress  of  the  work,  and 
the  following  information  should  be  recorded:  Date; 
time  of  day  of  each  entry;  day  or  night  work;  num¬ 
ber  of  men;  foreman;  condition  of  forms;  condition  of 
steel;  number  and  location  of  lights  (if  night  work) 
6 


Reinforced  Concrete  Construe tion. 

and  if  properly  lighted;  number,  time  and  location  of 
test  cubes  taken;  rate  of  mixing;  size  and  number  of 
batches;  proportions  of  mixture;  arrival  of  material; 
kind,  amount,  etc. 

Inspectors  will  be  required  to  fill  in  several  daily 
report  blanks  that  will  be  furnished. 

Inspectors  will  receive  further  written  instructions 
from  the  Engineer-in-Charge  from  time  to  time,  and 
will  attach  same  to  these  instructions  and  will  con¬ 
sider  them  a  part  of  same.  He  will  see  that  the  fol¬ 
lowing  specific  instructions  are  carried  out; 

FORMS. 

That  the  forms  are  properly  set  up  and  braced. 

That  the  concrete  face  of  the  forms  are  given  a. 
2oat  of  oil,  applied  with  a  brush. 

That  an  excess  of  oil  is  not  used. 

That  the  forms  are  cleaned  at  each  setting  and  re¬ 
lated  with  oil. 

That  the  forms  are  correctly  placed,  allowing  the 
lepth,  width  and  batter  called  for  on  the  plans. 

That  the  inside  of  the  forms  is  free  from  debris 
[shavings,  sawdust,  blocks  of  wood,  etc.)  just  pre¬ 
vious  to  pouring. 

That  the  forms  are  properly  held  together  with  No. 

1  wire  or  rods  of  suitable  dimensions,  and  temporary 
spacing  pieces  are  used  and  removed  when  the  con¬ 
crete  reaches  their  height. 

That  the  joints  formed  by  the  edges  of  the  lagging 
ire  tight,  so  that  grout  will  not  escape,  and  that  such 
lefects  are  remedied  by  the  use  of  plaster  of  paris, 
alking,  strips  of  wood  or  other  suitable  approved 
nethods. 

That  in  Bridge  Construction  the  arch  centers  are 
Dwered  sufficiently  to  allow  the  arch  ring  to  assume 
ts  permanent  set  before  spandrel  walls  are  poured, 
n  this  manner  reducing  the  possibilities  of  cracks 
ccurring  in  spandrel  walls  because  of  possible  exces- 
ive  settlement  in  crown  of  arch  ring. 

7 


Heinforced  Concrete  Construction. 


STEEL  REINFORCEMENT. 

That  the  correct  number  and  size  of  reinforcing 
'bars  are  used,  and  that  they  are  placed  as  shown  or 
plan. 

That  all  steel  used  is  free  from  loose  or  scaly  rust 
(A  thin  film  of  rust  will  not  cause  the  rejection  of  i 

bar.)  ; 

That  bars  covered  with  loose,  scaly  rust  are  cleaned 
with  a  stiff  wire  brush  or  given  a  pickling  bath  of  i\ 
sulphuric  acid  solution  (consisting  of  1  part  acid  t 
S  parts  of  water)  and  dipped  in  clean  water. 

That  the  intersection  of  the  rods  are  wound  with  s 
length  of  No.  18  wire  in  a  sufficient  number  of  place 
so  that  the  whole  steel  reinforcement  will  be  fabri 
cated  sufficiently  strong  and  rigid  to  withstand  th 
placing  of  concrete  about  the  steel  and  without  dis 
turbing  the  position  of  same. 

That  the  bars  are  speced  the  proper  distance  apar 
and  away  from  the  face  of  the  form  work  and  ar 
secured  properly  and  held  in  that  position  in  such 
manner  that  they  will  not  be  disturbed  by  the  placin 
of  concrete. 

That  in  bridge  construction  all  protruding  bars  froi 
piers  and  arches  to  which  other  bars  are  to  be  splice 
and  which  will  be  exposed  to  the  action  of  th 
weather  for  an  indefinite  period  are  protected  froi 
rusting  by  a  coat  of  thin,  neat  cement  grout. 

That  the  position  of  the  steel  is  not  disturbed  dui 
Ung  pouring. 

MIXING. 

Inspectors  will  be  required  to  carefully  and  coi 
tinuously  watch  the  mixing  of  the  concrete  and  tl 
desired  result  must  be  obtained  with  either  hand  < 
machine  mixing. 


8 


Reinforced  Concrete  Construction. 


Machine  Mixing. 

He  will  see  that  a  power,  batch  mixer  of  an 
ipproved  type  is  used,  constructed  and  operated  in 
such  a  manner  as  to  allow  proper  feeding  of  the 
materials,  the  thorough  mixing  of  the  component 
parts,  perfect  regulation  in  the  admission  of  water 
and  proper  discharging. 

That  the  required  number  of  turns  for  the  con¬ 
sistency  used  is  determined  by  trial  and  this  shall  con¬ 
stitute  the  minimum  number  of  turns  allowed  before 
discharging. 

That  the  entire  batch  is  discharged  each  time. 

That  the  concrete  shall  not  be  allowed  to  drop 
any  considerable  distance  when  discharging,  having  a 
tendency  to  separate  the  ingredients. 

That  the  mixer  is  flushed  with  water  and  thor¬ 
oughly  cleaned  before  being  allowed  to  stand  idle. 

That  the  concrete  is  delivered  to  point  of  disposal 
in  water  tight  carriers. 

Hand  Mixing. 

That  the  receptacles  used  for  measuring  sand  and 
broken  stone  are  of  the  correct  dimensions. 

That  the  sand  and  cement  are  mixed  dry  until  of 
a  uniform  color  before  adding  water. 

That  the  proper  amount  of  water  required  for  the 
consistency  used  is  determined  by  trial  and  this 
amount  used. 

That  the  stone  is  thoroughly  wetted  before  being 
incorporated  with  mortar. 

That  the  stone  is  spread  in  a  layer  of  uniform 
thickness  over  mortar  and  the  whole  turned  a  suffi¬ 
cient  number  of  times  so  that  all  grains  of  sand  and 
each  particle  of  stone  shall  be  coated  and  a  uniformly 
mixed  concrete  free  from  streaks  is  obtained. 

9 


Reinforced  Concrete  Construction. 


PLACING  CONCRETE. 

The  inspector  will  see  that  the  specified  propor¬ 
tions  of  material  are  used  in  mixing  the  concrete. 

That  the  concrete  is  of  the  proper  consistency. 

That  an  accurate  account  is  kept  of  the  number  of 
batches  mixed,  the  same  to  be  recorded  on  a  printed 
card  which  will  be  furnished  for  that  purpose. 

That  these  batch  record  cards  are  preserved  and 
filed  for  future  reference. 

That  in  placing  the  concrete  the  same  will  be  done 
in  a  careful  manner  and  precautions  taken  not  to 
allow  the  concrete  bucket  to  come  in  contact  with  the 
form  work. 

That  care  is  taken  not  to  jar  the  form  work  until 
the  concrete  work  is  hardened. 

That  in  making  a  bond  between  old  and  new 
work  care  is  taken  to  thoroughly  clean  the  surface  of 
old  concrete  (preferably  by  a  jet  of  steam),  and  that  a 
thin  layer  of  a  1  to  1  grout  is  spread  to  assist  in  mak¬ 
ing  a  good  bond. 

That  the  surface  of  the  concrete  which  is  to  be 
bonded  to  other  concrete  is  left  in  a  rough  condition, 
either  by  spreading  a  layer  of  broken  stone  over  the 
same,  ramming  half  the  depth  of  the  stone  into  the 
green  concrete  and  leaving  the  upper  half  of  the  stone 
protruding,  or  by  setting  in  strips  of  wood,  which 
when  removed,  will  form  a  groove  and  assist  in  mak¬ 
ing  a  good  bond. 

That  in  bonding  the  spandrel  wall  with  the  arch 
ring,  a  groove  or  ridge  is  formed  on  arch  rings  run¬ 
ning  under  and  with  spandrel  wall  to  prevent  water 
from  center  filling  to  run  through  and  down  the  face 
of  arch  ling  discoloring  same. 

10 


Reinforced  Concrete  Construction. 


That  in  placing  dry  concrete  the  same  is  thoroughly 
compacted  with  suitable  approved  iron  tamps. 

That  in  pouring  wet  concrete  the  same  is  thoroughly 
spaded,  rodded  and  worked  with  suitable  tools  suf¬ 
ficiently  to  cause  all  air  bubbles  to  escape,  to  work 
grout  to  face  of  form  work  filling  all  voids  and  show¬ 
ing  a  smooth,  well  mixed  concrete  free  from  voids 
when  forms  are  removed. 

That  a  fine  mixture  of  1  to  3  is  deposited  around 
and  among  the  bars,  and  that  it  is  thoroughly  worked 
in  and  around  the  bars  in  such  a  manner  that  the 
steel  will  be  completely  surrounded,  embedded  and 
covered. 

That  all  concrete  is  deposited  in  forms  within  30 
minutes  after  leaving  mixer. 

That  all  exposed  surfaces  of  concrete  are  kept  con¬ 
tinually  wet  for  a  period  of  10  days  after  the  removal 
of  forms. 

Care  should  be  taken  not  to  allow  the  first  concrete 
placed  to  appreciably  stiffen  or  set  before  the  re¬ 
maining  concrete  is  placed.  The  remedy  for  this  is 
to  occasionally,  as  often  as  is  necessary,  add  a  little 
more  concrete  to  that  already  placed  over  all  exposed 
surfaces. 

Great  attention  is  necessary  to  make  each  section 
(pier,  arch  ring  or  spandrel  wall)  monolithic  in  height, 
length  and  width.  Only  when  circumstances  render 
it  practically  unavoidable  may  the  work  be  stopped 
before  the  entire  section  is  completed. 


11 


Reinforced  Concrete  Construction. 


IN  BUILDING  CONSTRUCTION. 

The  inspector  is  required  to  see  that  the  following 
is  adhered  to: 

1.  The  right  size  and  number  of  rods  used. 

2.  The  rods  are  placed  as  designed. 

3.  The  U  bars  are  placed  correctly,  and  right  size 
and’  number  used. 

4.  Pouring  concrete  does  not  disturb  position  of 
steel. 

5.  The  bucket  is  lowered  lightly  on  floor. 

6.  The  bolts  in  bottom  of  beams  and  girders  for 
shaft  hangers  are  correct  for  position  per  plan. 

7.  No  shavings  cling  to  steel  coil  in  columns. 

8.  No  work  is  done  in  the  dark. 

9.  Concrete  is  properly  mixed. 

10.  Concrete  gets  under  rods  and  around  coiled 
couplings,  etc. 

11.  Wearing  surface  is  protected  by  boards  until 
set. 

12.  Wearing  surface  is  laid  to  level  grade. 

13.  If  forms  are  oiled  see  that  there  is  no  excess 
of  oil  used. 

14.  Concrete  is  moulded  within  thirty  minutes  after 
leaving  mixer. 

15.  In  mixing  concrete  in  cold  wreather,  aggregates 
are  heated. 

16.  Wearing  surface  is  laid  before  base  has  initial 
set. 

17.  The  exnansion  joints  are  properly  placed. 


12 


Reinforced  Concrete  Construction. 

18.  After  the  base  of  floor  is  poured  it  is  protected 
from  heat  or  cold. 

19.  Concrete  in  bay  is  carried  to  center  of  girder. 
Bay  must  be  completed. 

20.  Coil  couplings  are  properly  located  and  proper¬ 
ly  installed. 

21.  All  steel  is  clean,  and  entirely  free  from  all 
dirt  and  loose  rust. 

22.  In  joining  new  work  on  old,  hose  is  played  on 
old  where  new  work  will  join  on,  and  wash  with 
cement  grout. 

23.  All  forms  are  well  swept  and  free  from  debris 
before  pouring  concrete  into  same. 

24.  Pouring  beams,  girders,  columns,  etc.,  is  a  con¬ 
tinuous,  or  as  nearly  so  as  possible,  operation  until 
same  is  completed. 

25.  Concrete  is  kept  wet  continually  for  a  period 
of  two  weeks  after  being  poured. 

26.  Fires  are  kept  burning  in  salamanders  on  floor 
below  whenever  concrete  is  poured  in  cold  weather. 

27.  Before  finished  floor  is  laid  the  surface  of 
concrete  which  is  to  receive  the  wearing  surface  is 
properly  compacted  or  tamped. 

28.  Concrete  is  properly  “cut”  in  all  beams,  girders 
and  columns  before  the  base  of  floor  is  laid. 

29.  No  aggregates  other  than  called  for  in  the  speci¬ 
fications  are  moulded  in  the  forms. 

30.  Concrete  should  be  well  sliced  and  puddled  into 
all  girders,  beams,  columns,  etc. 

31.  Notes  should  be  made  of  any  cracks  that  may 
appear  in  concrete  due  to  forms  expanding,  contract¬ 
ing  or  settling.  Note  condition  of  forms  before  con¬ 
crete  is  poured. 


13 


Reinforced  Concrete  Construction. 


PROPORTIONING  THE  CONCRETE. 

The  proportion  of  concrete  used  depends  upon  the 
class  of  work  for  which  it  is  intended  and  varies  be- 
tween  a  1—1%— 3  and  a  1-4-8  mixture.  For  light 
columns  and  thin  roof  beams  and  for  ornamental  work 
a  i — iy2 — 3  mixture  is  suitable. 

For  beams,  floor  slabs  and  columns  a  1  2  4  or  a 

1 — 2 — 5  mixture  is  suitable. 

For  non-bearing  walls,  reinforced  piers  and  foot¬ 
ings  a  1—3—5  mixture  is  suitable. 

For  mass  concrete,  a  1 — 3 — 6  to  1 — 4  8  mixture  is 
used. 

What  might  be  determined  as  an  ideal  concrete  is 
where  the  vol.  of  cement  slightly  exceeds  the  voids  in 
the  sand  and  the  vol.  of  mortar  slightly  exceeds  the 
voids  in  the  stone.  If  this  were  followed  out  by  tests 
and  the  actual  voids  in  the  sand  and  stone  determined 
it  would  probably  develop  that  a  1—3—6  mixture  ^vould 
be  suitable  where  a  1—2—4  mixture  was  being  used 
and  would  effect  a  considerable  saving. 

If  sand  is  coarse  and  of  graded  sized  grains  and 
the  broken  stone  is  proportioned  by  the  use  of  sizes 
varying  from  IV2  in.  to  %  in*  so  that  the  voids  would 
be  reduced  to  say  20  per  cent.,  a  very  dense  and  suit¬ 
able  concrete  could  be  obtained  with  a  1  3  6  mix¬ 

ture  and  equal  in  every  way  to  a  1 — 2 — 4  mixture  made 
up  of  aggregates  the  voids  of  which  are  not  deter¬ 
mined. 

For  finishing  floors  a  1 — to — 1  to  a  1 — to — 2  mixture 
of  sand  and  cement  is  used. 


14 


Reinforced  Concrete  Construction. 


COST  OF  CONCRETE. 

Assume  1 — 2 — 4  mixture. 

Cement  $2.00  per  bbl.  )  _  ..  ,  .,  ... 

Sand  $1.00  per  cu.  yd.  Delivered  on  the  site  of  the 

Stone  $1.50  per  cu.  yd.  >  worK* 

1  bbl.  cement — 3.8  eft.  Sand  30  per  cent,  voids. 
Stone  45  per  cent  void. 

1  cu.  yd.  concrete  requires. 


I. 54  bbls.  cement  at  2.00 .  $3.08 

II. 7  eft.  sand  at  1.00  c.  y . 43  1-3 

23.4  eft.  stone  at  1.50  c.  y .  0.86  2-3 


Cost  of  materials  per  c.  y .  $4.38 

Cost  of  mixing  and  handling  depends  on  facilities 
for  getting  material  to  mixer  and  away  from  mixer. 
The  actual  cost  of  mixing  with  machine  is  very  small. 
With  good  supervision  and  best  layout  of  plant  the 
cost  per  cubic  yard  should  average  about  $1.50  for 
handling,  mixing  and  placing  concrete  in  building  con¬ 
struction.  This  gives  a  total  of  $5.88  per  cu.  yd.  for  a 
1 — 2 — 4  mixture  of  concrete  exclusive  of  formwork 
and  reinforcement  with  material  at  the  above  prices. 
The  cost  per  cu.  yd.  of  any  mixture  used  can  be  de¬ 
termined  in  this  manner  knowing  the  cost  of  each 
kind  of  material  delivered  on  the  work. 

COST  OF  BUILDING. 

Factory  buildings  of  reinforced  concrete,  including 
windows,  doors  and  roofing,  cost  from  8  to  16  cents 
per  cubic  foot  of  contents. 


15 


Reinforced  Concrete  Construction. 


COST  OF  REINFORCEMENT. 

The  amount  and  cost  of  reinforcement  greatly  de¬ 
pends  upon  the  system  used  which  varies  in  amount 
and  grade  of  steel  used.  The  deformed  bars  and 
other  patented  forms  of  reinforcement  necessarily 
increase  the  cost  of  manufacture  over  plain  and  com¬ 
mercial  shapes  which  when  used  usually  require  a 
larger  percentage  to  attain  the  same  requirement 
owing  to  its  lower  tensile  strength  and  bond. 

In  estimating  the  cost  of  the  reinforcement  required 
with  any  degree  of  accuracy  it  is  necessary  to  deter¬ 
mine  the  exact  amount  of  steel  required  as  shown  on 
plans  and  with  a  price  per  ton,  determine  exactly  the 
entire  cost  of  reinforcement  for  the  building.  The 
price  for  steel  for  this  purpose  varies  from  2  cents  to 
5  cents  per  lb. 

Floors  require  from  2y2  to  6  lbs.  of  reinforcement 
according  to  the  floor  load  carried,  including  slabs, 
beams,  girders,  columns,  lintels  and  footings. 

COST  OF  FORMWORK. 

The  cost  of  formwork  varies  with  the  class  of  work 
and  the  number  of  times  it  can  be  used. 

The  formwork  on  a  small  building  costs  more  per 
cubic  yard  of  concrete  placed  than  the  formwork  in  a 
large  building,  where  it  can  be  re-used  as  many  as 
four  times  with  a  very  small  percentage  of  loss  or 
waste,  because  of  the  similarity  of  dimensions  in  the 
various  structural  members. 

Formwork  may  cost  from  fifty  cents  to  two  dollars 
per  cubic  yard  of  concrete  placed,  depending  on  the 
volume  of  concrete  the  forms  retain  and  the  simplicity 
or  irregularity  of  same,  and  the  amount  of  bracing 
required  to  hold  same  in  place. 


16 


Reinforced  Concrete  Construction. 


STRIPPING  FORMWORK. 

To  determine  if  concrete  has  sufficiently  hardened 
to  allow  removal  of  forms  several  methods  are 
adopted.  Probably  the  best  and  most  scientific  is  to 
take  test  cubes  on  each  section  of  floor  poured  and 
set  a  minimum  compressive  strength  that  it  must 
attain  before  removal  of  forms,  and  when  the  cubes 
show  the  strength  by  test  it  is  safe  to  remove  form- 
work  on  the  section  from  which  cube  was  taken.  An¬ 
other  method  is  to  attempt  to  drive  a  20  penny  wire 
nail  into  the  concrete  and  if  nail  bends  before  a  pene¬ 
tration  of  2  inches  is  reached,  under  medium  heavy 
blows  with  a  carpenter’s  ordinary  claw  hammer,  it  is 
safe  to  remove  forms. 

It  is  usually  safe  to  remove  forms  from  non-bearing 
walls,  etc.,  in  five  days  from  May  to  October,  and 
eight  days  from  October  to  May.  For  columns  and 
floors,  eight  to  fifteen  days  from  May  to  October,  and 
ten  to  twenty  days  from  October  to  May. 

WATERPROOF  CONCRETE. 

It  has  been  determined  in  the  construction  of 
reservoirs,  etc.,  that  an  admixture  of  about  ten  per 
cent,  of  hydrated  lime  to  the  amount  of  cement 
used  will  make  a  rich  mixture  of  concrete  water¬ 
proof.  There  are  also  a  number  of  patented  mixtures, 
which  when  added  to  the  concrete  during  mixing 
or  washed  on  the  surface  of  the  concrete  after  the 
removal  of  forms,  have  a  waterproofing  effect. 

When  it  is  desired  to  obtain  a  concrete  that  is 
impervious  to  water,  a  rich  mixture  of  not  more  than 
1 — 2 — 4  should  be  used,  the  broken  stone  or  screened 
graved  to  be  clean  and  range  in  size  from  %  in.  to  % 
in.  in  diameter. 

It  has  been  determined  that  concrete  reaches  its 
maximum  strength  in  about  three  years.  To  retard 
the  setting  of  cement,  which  is  desirable  at  times  in 
order  that  it  will  attain  greater  strength  ultimately, 
add  three  pounds  slacked  lime  and  a  solution  of  com¬ 
mon  salt  and  water,  using  two  pounds  to  the  gallon, 
and  add  one  gallon  of  the  solution  to  each  barrel  of 
cement  used. 


1 


Reinforced  Concrete  Construction. 


FORMULAS 

For  the  Design  of  Reinforced  Concrete  Beams. 


Mb=Ultimate  bending  moment  in  inch  lbs. 

wl2=Mb  simple  beam  uniformilv  loaded. 

~8~ 

wl2=Mb  continuous  beam  uniformily 
io  loaded. 

w=weight  on  beam  per  lineal  ft. 

l=length  of  beam  from  cen.  to  cen.  of  sup¬ 
ports. 

Mr=Mb. 

Mr=90  bd2. 

b= width  of  beam. 

d=depth  of  beam. 

With  steel  of  an  elastic  limit  of 
54000  lbs.  use  an  area  of  75%  bd. 

With  steel  of  an  elastic  limit  of 
35000  lbs.  use  1. 00  to  1.25%  bd. 


18 


Reinforced  Concrete  Construction. 


TABLE  OF  SAFE  LOADS  FOR 
REINFORCED  CONCRETE  COLUMNS. 


Stress  per  Sq  Inch 


Size  of  Col 

300  lbs. 

400  lbs. 

500  lbs. 

8x8 

19,200 

2  5,600 

32,000 

IOXIO 

30,000 

40,000 

50,000 

12X12 

43,200 

57,600 

72,000 

14X14 

58,800 

78,400 

98,000 

l6xi6 

76,800 

102,400 

128,000 

l8xi8 

97,200 

129,600 

162,000 

20X20 

120,000 

160,000 

200,000 

22X22 

145,200 

193,600 

242,000 

24x24 

172  .  800 

230,400 

288,000 

26x26 

202,800 

270,400 

338,000 

28x28 

235,200 

313,600 

392,000 

3OX3O 

270,000 

360,000 

450,000 

32X32 

307,200 

409,600 

512,000 

34X34 

346,800 

462,400 

578,000 

36x36 

388,800 

518,400 

648,000 

Steel 

Stress  per  Sq. 

Inch 

Rods 

Area 

4,500 

6,000 

7,500 

4— 

0.785 

3,532 

4,710 

5,887 

4—  %" 

1.227 

5,521 

7.362 

9,202 

4-  %" 

1.767 

7,951 

10,602 

13,252 

4 —  %" 

2.405 

9,202 

12,270 

15,337 

4—1" 

3-I4I 

14,134 

18,846 

23,557 

4-1  Vs" 

3-976 

17,892 

23.856 

29,820 

4—1 

4.908 

22,086 

29,448 

36,810 

19 


Materials  Required  for  i  Cubic  Yard  of 
Concrete  with  %  Inch  Stone 


Proportions  of 
Mixture 

Required  for 

1  cu.  yd. 

Cement 

Sand 

Stone 

Cement  1 
bbls. 

Sand 
c.  yds. 

Stone 
c.  yds. 

I 

i-5 

3 

1.85 

O.42 

0.84 

I 

2.0 

4 

1 .46 

!  0.44 

0.89 

I 

2.0 

5 

r  .27 

0.39 

O.97 

1 

2-5 

5 

1. 19 

0.46 

0.91 

I 

3-o 

5 

1. 11 

0.51 

0.85 

1 

3-o 

6 

1 .01 

0.46 

O.92 

I 

4.0 

8 

0.77 

0.47 

0.93 

Concrete  with  2^  Inch  Stone  and  under 


Proportions  of 
Mixture 

Required 

1  cu.  yd 

for 

Cement 

Sand 

Stone 

Cement 

bbls. 

Sand 
c.  yds. 

Stone 
c.  yds- 

I 

1-5 

3 

1 .90 

0.43 

0.87 

1 

2.0 

4 

1 .48 

0.45 

O.90 

I 

2.0 

5 

I.29 

o,39 

O.98 

I 

2.5 

5 

1 .2  I 

0.46 

O.92 

I 

3-o 

5 

I*I4 

0.52 

O.87 

I 

3-o 

6 

I  .02 

0.47 

o-93 

I 

4.0 

8 

O.78 

i 

0.48 

0-95 

Materials  Required  for  1  Cu.  Yd.  Mortar 
Parts  of  Sand  mixed  with  one  part  Cement 


1.0 

1.5 

2.0 

2.5 

3.0 

3.5 

4.0 

5.0 

Sbls.  Cement 

4.70 

3.70 

3.04 

2.58 

2.21 

1.94 

1.72 

1.41 

Cn.  yds.  Sand 

0.7L 

0.84 

0.92 

0.98 

1.01 

1.03 

1.05 

1.08 

20 


Reinforced  Concrete  Construction. 


CONCRETE  FOOTINGS. 


Plain  concrete  footings  for  earth  pressure  of 

1  ton  per  sq.  ft.  height  -  0.5  (base — width  col.) 

2  tons  “  “  u  “  =  0.75(base— width  col.) 

3  “  “  “  u  “  ^O^hase — width  col.) 

4  “  “  “  “  “  -  base — width  col.) 

Step  footings  in  courses 
Reinforced  concrete  footings  for  earth  pres¬ 
sure  of 

1  ton  per  sq.  ft.  height  =  0. 175(base — width  col.) 


2  tons  “  “  “ 

“  »0.35  (base — width  col.) 

3  «  -  <<  “ 

‘  ‘  =  0.525(base — width  col .) 

4  “  “  “  “ 

-0.70  (base — width  col.) 

For  reinforcement  use  rods  of  a  diameter 
equal  to  base-r-100  spaced  10  times  their  di¬ 
ameter  apart  and  one-tentli  of  height  from 
bottom  of  footing. 


21 


To  Determine  Quantity  of  Materials 
Required  for  a  Known  Amount  of  Concrete 
Materials  required  for  1000  cu.  yds.  of  1 — 2 — 4 
concrete  1  bbl.  cement  3.8  cu.  ft.  sand  30%  voids, 
stone  45%  voids. 

1  bbl.  cement  3  8  cu.  ft.  3.80  c.f. 

2  bbls.  sand  7.6  c.f.  30%  voids  5.32  c.t. 

4  bbls.  stone  15.2  c.f.  45%  voids  8.36  c.f. 

loose  material  26.6  c.f.  in  place  17.48  c.f. 

1  bbl.  cement  produces  17.48  c.f.  concrete. 

1  cu.  yd.  concrete  requires  (27.0-4-17.48)  -  1.54  bl. 
cement. 

7.6  c.f.  sand  produces  17.48  c.f.  concrete. 

1  c.  y.  concrete  requires  (27.0-1-17.48)7.6=11.7  c  f. 
sand. 

15.2  c.f.  stone  produces  17.48  c.f.  concrete. 

1  cu.  yd.  concrete  requires  (27.0-1-17.48)  15.2  = 
23.4  c.f.  stone. 

1000  cu.  yds.  concrete  require  1000x1.54  *  1540  bl. 
cement. 

1000  cu.  yds.  concrete  require  1000x11.70  = 
11700  c.f.  sand. 

1000  cu.  yds.  concrete  require  1000x23.4  =  23400  cf. 
stone. 

Total  material  required  for  1000  cu.  yds,  con¬ 
crete  1540  bbls.  cement,  433  3  cu.  yds.  sand, 

866.6  cu.  yds.  stone. 

RECORD  OF  TEST  CUBES. 

Cube  No . 

Where  taken  . *. . 

Date  . 

Time  of  day . . 

Mixer  . . . . . . 

Cement  . 

Remarks  . 

Cube  taken  by . 

Signature. 

Where  stored  . 

Date  of  test... . 

Strength  of  cubes  in  tons . 

Strength  per  sq.  in.  in  pounds . 

Remarks  . 


22 


meg 


